Sparkling blue sapphire stones evoke a sense of coldness, yet they actually originate deep within volcanoes.
Over the years, sapphire has been discovered in large volcanoes such as the Eifel. There, magma from the Earth’s crust rises to the surface over long periods, creating sodium- and potassium-rich solutions.
Researchers have unraveled the mysterious origins of sapphire stones (Photo: Getty).
However, some sapphires are also found beneath riverbeds in the form of resilient crystals that have been washed away from solid rock formations.
This leaves the exact origin of sapphire a mystery to geologists.
In a recent study, scientists confirmed once again that these blue stones are formed through volcanic activity, where extreme processes heat and compress aluminum oxide in the crust, resulting in a crystalline form known as corundum—the main mineral that composes sapphire.
The presence of sapphire stones on the Earth’s surface and beneath riverbeds is due to their ascent along magma flows, in a hydraulic elevator-like system.
To reach this conclusion, the research team collected 223 tiny sapphires from the Eifel volcano and applied secondary ion mass spectrometry for analysis.
They focused on key characteristics of this stone, including the ratio of rutile and zircon trapped within the sapphire during its formation and the ratios of oxygen isotopes in aluminum oxide.
By studying the ratios of these isotopes, the researchers determined that the sapphires in Eifel originated from approximately 7 km below the Earth’s surface.
Meanwhile, uranium-lead dating methods indicated that they formed concurrently with volcanic activity, which eventually brought them to the surface.
The researchers also established that the “famous” blue color of sapphire comes from titanium and iron staining corundum. If the stone’s composition consists only of iron, it will produce yellow or green sapphires.
In contrast, the presence of chromium in ruby stones gives them their red color.